// createBlock creates a new block building from the previous block.
func createBlock(prevBlock *btcutil.Block, inclusionTxs []*btcutil.Tx,
	blockVersion int32, blockTime time.Time,
	miningAddr btcutil.Address, net *chaincfg.Params) (*btcutil.Block, error) {

	prevHash := prevBlock.Hash()
	blockHeight := prevBlock.Height() + 1

	// If a target block time was specified, then use that as the header's
	// timestamp. Otherwise, add one second to the previous block unless
	// it's the genesis block in which case use the current time.
	var ts time.Time
	switch {
	case !blockTime.IsZero():
		ts = blockTime
	default:
		ts = prevBlock.MsgBlock().Header.Timestamp.Add(time.Second)
	}

	extraNonce := uint64(0)
	coinbaseScript, err := standardCoinbaseScript(blockHeight, extraNonce)
	if err != nil {
		return nil, err
	}
	coinbaseTx, err := createCoinbaseTx(coinbaseScript, blockHeight,
		miningAddr, net)
	if err != nil {
		return nil, err
	}

	// Create a new block ready to be solved.
	blockTxns := []*btcutil.Tx{coinbaseTx}
	if inclusionTxs != nil {
		blockTxns = append(blockTxns, inclusionTxs...)
	}
	merkles := blockchain.BuildMerkleTreeStore(blockTxns)
	var block wire.MsgBlock
	block.Header = wire.BlockHeader{
		Version:    blockVersion,
		PrevBlock:  *prevHash,
		MerkleRoot: *merkles[len(merkles)-1],
		Timestamp:  ts,
		Bits:       net.PowLimitBits,
	}
	for _, tx := range blockTxns {
		if err := block.AddTransaction(tx.MsgTx()); err != nil {
			return nil, err
		}
	}

	found := solveBlock(&block.Header, net.PowLimit)
	if !found {
		return nil, errors.New("Unable to solve block")
	}

	utilBlock := btcutil.NewBlock(&block)
	utilBlock.SetHeight(blockHeight)
	return utilBlock, nil
}

// TestMerkle tests the BuildMerkleTreeStore API.
func TestMerkle(t *testing.T) {
	block := btcutil.NewBlock(&Block100000)
	merkles := blockchain.BuildMerkleTreeStore(block.Transactions())
	calculatedMerkleRoot := merkles[len(merkles)-1]
	wantMerkle := &Block100000.Header.MerkleRoot
	if !wantMerkle.IsEqual(calculatedMerkleRoot) {
		t.Errorf("BuildMerkleTreeStore: merkle root mismatch - "+
			"got %v, want %v", calculatedMerkleRoot, wantMerkle)
	}
}

// UpdateExtraNonce updates the extra nonce in the coinbase script of the passed
// block by regenerating the coinbase script with the passed value and block
// height.  It also recalculates and updates the new merkle root that results
// from changing the coinbase script.
func UpdateExtraNonce(msgBlock *wire.MsgBlock, blockHeight int32, extraNonce uint64) error {
	coinbaseScript, err := standardCoinbaseScript(blockHeight, extraNonce)
	if err != nil {
		return err
	}
	if len(coinbaseScript) > blockchain.MaxCoinbaseScriptLen {
		return fmt.Errorf("coinbase transaction script length "+
			"of %d is out of range (min: %d, max: %d)",
			len(coinbaseScript), blockchain.MinCoinbaseScriptLen,
			blockchain.MaxCoinbaseScriptLen)
	}
	msgBlock.Transactions[0].TxIn[0].SignatureScript = coinbaseScript

	// TODO(davec): A btcutil.Block should use saved in the state to avoid
	// recalculating all of the other transaction hashes.
	// block.Transactions[0].InvalidateCache()

	// Recalculate the merkle root with the updated extra nonce.
	block := btcutil.NewBlock(msgBlock)
	merkles := blockchain.BuildMerkleTreeStore(block.Transactions())
	msgBlock.Header.MerkleRoot = *merkles[len(merkles)-1]
	return nil
}

//.........这里部分代码省略.........
			minrLog.Tracef("Skipping tx %s due to error in "+
				"ValidateTransactionScripts: %v", tx.Sha(), err)
			logSkippedDeps(tx, deps)
			continue
		}

		// Spend the transaction inputs in the block transaction store
		// and add an entry for it to ensure any transactions which
		// reference this one have it available as an input and can
		// ensure they aren't double spending.
		spendTransaction(blockTxStore, tx, nextBlockHeight)

		// Add the transaction to the block, increment counters, and
		// save the fees and signature operation counts to the block
		// template.
		blockTxns = append(blockTxns, tx)
		blockSize += txSize
		blockSigOps += numSigOps
		totalFees += prioItem.fee
		txFees = append(txFees, prioItem.fee)
		txSigOpCounts = append(txSigOpCounts, numSigOps)

		minrLog.Tracef("Adding tx %s (priority %.2f, feePerKB %.2f)",
			prioItem.tx.Sha(), prioItem.priority, prioItem.feePerKB)

		// Add transactions which depend on this one (and also do not
		// have any other unsatisified dependencies) to the priority
		// queue.
		if deps != nil {
			for e := deps.Front(); e != nil; e = e.Next() {
				// Add the transaction to the priority queue if
				// there are no more dependencies after this
				// one.
				item := e.Value.(*txPrioItem)
				delete(item.dependsOn, *tx.Sha())
				if len(item.dependsOn) == 0 {
					heap.Push(priorityQueue, item)
				}
			}
		}
	}

	// Now that the actual transactions have been selected, update the
	// block size for the real transaction count and coinbase value with
	// the total fees accordingly.
	blockSize -= wire.MaxVarIntPayload -
		uint32(wire.VarIntSerializeSize(uint64(len(blockTxns))))
	coinbaseTx.MsgTx().TxOut[0].Value += totalFees
	txFees[0] = -totalFees

	// Calculate the required difficulty for the block.  The timestamp
	// is potentially adjusted to ensure it comes after the median time of
	// the last several blocks per the chain consensus rules.
	ts, err := medianAdjustedTime(chainState, timeSource)
	if err != nil {
		return nil, err
	}
	requiredDifficulty, err := blockManager.CalcNextRequiredDifficulty(ts)
	if err != nil {
		return nil, err
	}

	// Create a new block ready to be solved.
	merkles := blockchain.BuildMerkleTreeStore(blockTxns)
	var msgBlock wire.MsgBlock
	msgBlock.Header = wire.BlockHeader{
		Version:    generatedBlockVersion,
		PrevBlock:  *prevHash,
		MerkleRoot: *merkles[len(merkles)-1],
		Timestamp:  ts,
		Bits:       requiredDifficulty,
	}
	for _, tx := range blockTxns {
		if err := msgBlock.AddTransaction(tx.MsgTx()); err != nil {
			return nil, err
		}
	}

	// Finally, perform a full check on the created block against the chain
	// consensus rules to ensure it properly connects to the current best
	// chain with no issues.
	block := btcutil.NewBlock(&msgBlock)
	block.SetHeight(nextBlockHeight)
	if err := blockManager.CheckConnectBlock(block); err != nil {
		return nil, err
	}

	minrLog.Debugf("Created new block template (%d transactions, %d in "+
		"fees, %d signature operations, %d bytes, target difficulty "+
		"%064x)", len(msgBlock.Transactions), totalFees, blockSigOps,
		blockSize, blockchain.CompactToBig(msgBlock.Header.Bits))

	return &BlockTemplate{
		block:           &msgBlock,
		fees:            txFees,
		sigOpCounts:     txSigOpCounts,
		height:          nextBlockHeight,
		validPayAddress: payToAddress != nil,
	}, nil
}